This project brings a collaborator with much expertise in calcium signaling in cardiac cells into collaborations with the Resource Center. This project aims to understand the role of calcium ion concentration in both the cytosol and in the SR in regulation of Ca2+ sparks. The role of the proposed National Resource in this project is to provide enhanced imaging capability via the Noran rapid scanning confocal microscope and the 2-photon excitation scanning microscope. Additionally, the application of Virtual Cell modeling to this project is expected to play a major role.